The present invention refers to a method for measuring a dimension of a body, the image of said body being projected onto a measuring sensor, and said dimension being detected by electrooptical means. Known measuring methods are limited to the detection of two dimensions at the most, i.e. the measuring sensor is capable of evaluating the two-dimensional image of a body at the most. In many cases, however, it is desirable to detect three dimensions of the body in order to evaluate its size in three dimensions, or its volume and weight, respectively. Such a detection of the actual size is e.g. desired in sorting processes, in particular for sorting fruit and field crops, especially potatoes. The hitherto usual sorting method, wherein potatoes are sized by dropping through square openings of graded sizes, cannot satisfy in so far as particularly slim potatoes are attributed to a given size although they may under given circumstances have the double volume of spherical potatoes in the same size class. However, the detection of three dimensions of bodies has been complicated and in certain cases impossible even under increased expenditure.